European Patent Application No. 0 302 660 describes a fuel injection valve, at the downstream end of which is provided an adaptor into which flows fuel which comes from an outlet orifice and which, at the downstream end of the adaptor, itself strikes a plane metal disk having meshes for the purpose of breaking up the fuel. The metal disk is arranged in such a way that an airstream, via holes in the adaptor, ensures that fuel drops caught on the metal disk are torn away. A better atomizing quality is therefore achieved only when the fuel is surrounded by an airstream near the metal disk, although an exact spray geometry cannot be achieved by means of this airstream. The square meshes of the metal disk are of equal size on account of the uniform network and form a checked pattern which is symmetrical in all directions. The network of the metal disk is therefore of grid-like design, the network having no variations in cross section in the axial direction. Consequently, no special atomizing edges are provided.
Moreover, it is described in German Patent Application No. DE 2 723 280 to design on a fuel injection valve, downstream of a metering orifice, a fuel breakup member in the form of a plane thin disk which has a multiplicity of arcuate narrow slits. The arcuate slits, which are made in the disk by etching, ensure by means of their geometry, that is to say by means of their radial width and their arc length, that a fuel film which breaks up into small droplets is formed. The etching operation for making the slits is cost-intensive. Furthermore, the individual slit is have to be made highly accurately relative to one another, in order to ensure that the fuel is broken up in the desired way. The arcuate slits each have a constant aperture width over the entire axial extension of the breakup member. Atomization is therefore to be improved by means of the horizontal radial geometry of the slits in the plane of the breakup member.
The so-called LIGA process for the production of micromechanical components is described in, for example, Heuberger: "Mikromechanik" ("Micromechanics"), Springer-Verlag 1989, page 236 ff., and Reichl: "Micro System Technologies 90", Springer-Verlag 1990, page 521 ff. This process involves the steps of lithography, electroforming and cast taking (Lithographie, Galvanoformung, Abformung). Extremely accurate microstructures can thereby be produced simply in a very good quality and in large quantities. In contrast to erosion processes for example, an incomparably wider diversity of geometries can be effected by means of the LIGA process.
A device for improving fuel atomization by feeding air into the liquid fuel upstream of an injection nozzle is also described in International Application No. WO 92/13188. The feed of the air takes place on the suction side, via an air-jet pump, under negative pressure into a fuel pump. The blowing-in of the air is carried out via a single bore into the fuel flow path, so that the fuel is enriched with inflowing air bubbles always at one point only.